The recent development in the field of superhard materials with Vickers hardness of ⩾40 GPa is reviewed. Two basic approaches are outlined including the intrinsic superhard materials, such as diamond, cubic boron nitride, carbonitrides, etc. and extrinsic, nanostructured materials for which superhardness is achieved by an appropriate design of their microstructure. The theoretically predicted high hardness of has not been experimentally documented so far. Ceramics made of cubic boron nitride prepared at high pressure and temperature find many applications whereas thin films prepared by activated deposition from the gas phase are still in the stage of fundamental development. The greatest progress has been achieved in the field of nanostructured materials including superlattices and nanocomposites where superhardness of ⩾50 GPa was reported for several systems. More recently, nanocomposites with hardness of 105 GPa were prepared, reaching the hardness of diamond. The principles of design for these materials are summarized and some unresolved questions outlined.

Low pressure (<50 mTorr) electron cyclotron resonanceplasma sources are being developed for downstream etching and deposition and for production of radicals for surface treatment. The spatial coupling of microwave radiation to the plasma is a concern due to issues related to the uniformity of dissociation, electron heating, and ultimately process uniformity. To investigate these issues, a finite-difference-time-domain simulation for microwave injection and propagation has been developed, and has been incorporated as a module in the two-dimensional Hybrid Plasma Equipment Model. Results from parametric studies of plasmas suggest that obtaining uniform fluxes to the substrate may require a power deposition profile that is peaked off axis. An increase in power deposition tends to reinforce nonuniformities in the ion flux profile. At higher pressures (>10 mTorr) the sensitivity of the ion flux to the substrate to the angle of the magnetic field at the substrate decreases, while the uniformity of the ion flux improves. Due to the dependence of the collision frequency on electron temperature, losses from cross-field diffusion are enhanced in both the low and high pressure regimes. Results also suggest that there is an optimal pressure for maximizing both the magnitude of the ion flux to the substrate surface and its uniformity.

The etching of silicon in remote microwave discharges fed with has been investigated. In situellipsometry and x-ray photoelectron spectroscopy(XPS) were used to monitor surfaceeffects, while mass spectrometry was used to monitor the gas phase dynamics. Varying the microwave power from 600 to 1400 W has little effect, due to the near complete dissociation of the even at lower powers. For discharges containing pure the poly-Si etch rate increases linearly with flow. When a low proportion of is added to the discharge, the etch rate increases quickly to its maximum of ∼700 nm/min. With further addition, this etch rate decreases below that observed for pure processing. The fluorine concentration in the processing region decreases for all additions by a dilution effect. For pure discharges,XPS measurements reveal 1–2 nm thick, highly fluorinated reaction layers with a gradual loss of fluorine content as the flow is increased. Specimens processed with both and show much less surface fluorination that decreases with increasing content in the feed gas. At the etch rate maximum, the observed N signal is also maximized. The reaction layer thickness increases with added and continues to more than 10 nm at ratios greater than unity. We discuss the enhanced reactivity of the modified Si surface and compare our results with the role of admixed into the system. We also injected NO directly into the effluent of and discharges. For fluorine rich discharges, NO removes the modified surface layer on Si and provides for an enhanced etch rate. In the oxygen rich regime, NO injection can increase both the etch rate and the reaction layer thickness. We will present a mechanism for the enhanced etching of Si in the presence of fluorine, oxygen and the NO molecule.

Positive ions and radicals in and high density discharges were measured using a direct-line-of-sight mass spectrometer. The ion energy distributions of the dominant ions were measured as a function of process conditions. Appearance potential mass spectrometry was performed to measure trends of the radical densities. For plasmas and are the most abundant neutral and ionic species, respectively. is the most abundant neutral species for a plasma, whereas and are the most abundant ionic species at 600–1000 and 1400 W, respectively. Erosion of the quartz coupling window is an important contaminant source for our inductively coupled plasma system. For comparison, downstream mass spectrometry was also applied using a closed ion source system since this approach is of interest for real-time monitoring and control. Endpoint detection for Si and film etching in a plasma was investigated using the downstream mass spectrometer system and compared with data obtained simultaneously using the direct-line-of-sight mass spectrometer and optical emission spectroscopy. It was found that the downstream mass spectrometer system can be used for endpoint detection during over Si selective etching. The signal changes of different species measured by these techniques for different and Si etching processes as a function of time are reported and compared.

Mass spectrometry and appearance potential mass spectrometry (APMS) have recently gained importance for detection and quantitative measurements of reactive radical species in plasmas using line-of-sight sampling of reactive species. In this work, we have characterized the contributions to the mass spectrometer signal from the line-of-sight “beam” component and the background component of the species in the ionizer of the mass spectrometer. The beam signal is proportional to the number density of the species in the plasma, while the background component of the signal depends on various factors like the vacuum system design and pump speeds. Single differential pumping of the mass spectrometer is found to be inadequate as the background signal dominates the beam signal for radical and stable neutral species. The beam to background ratio for radicals is smaller than 0.25 and the large background signals of the species of interest necessitates implementation of modulated beam mass spectrometry using a mechanical chopper in the beam path. The uncertainty in the beam component measurement is found to be as large as ±180%. High beam-to-background signal ratio is achieved using three stages of differential pumping, and this vastly reduces the uncertainty in the beam component measurement to less than ±10%.

Supersonic pulse, plasma sampling mass spectrometry has been used to probe electron cyclotron resonancemicrowaveplasmas consisting of 2% ethane in hydrogen and 2% ethane in deuterium. The overall hydrocarbon chemistry and interconversion of species within these plasmas were determined by comparing the composition of these two chemically equivalent plasmas. The ethane in hydrogen plasma is shown to consist of 58% unreacted ethane 16% ethylene 12% acetylene 9% methane with the remaining 4% of the counts attributed to the ethylene radical species and the ethane radical species The mass spectrum of the analogous deuterium plasma reveals the ethane to remain entirely undeuterated, while the ethylene and acetylene exhibit significant deuteration. The observation of significantly deuterated ethylenes indicates a new reaction channel is available in these ethane-based plasmas, that is not available to hydrocarbon plasmas based on acetylene or ethylene. Specifically, the reaction of the ethane radical with a hydrogen atom results in the cleavage of the carbon–carbon bond forming two methyl radicals Once formed, the methyl radicals may undergo repeated cycles of hydrogen (deuterium) atom additions and abstractions (analogous to those previously observed for acetylene) before recombining to yield the deuterated ethane radicals which then by abstraction of a hydrogen (or deuterium) forms the observed deuterated ethylenes. Overall, the chemistry of these hydrocarbon plasmas is shown to be completely consistent with the neutral molecule reactions previously observed in combustion chemistry literature.

We investigated the differences in radical generation due to chemical bonding of fluorocarbon gas molecules in the plasma. We found that dissociation of the bond is five times easier than that of the C–C bond in a fluorocarbon gas plasma. As a result, a plasma could generate a higher density of radicals than a plasma. Additionally, the same dissociation processes occurred in the and plasma, which both have the bond and C–C bond in their molecules. In the plasma, the density of generated radicals was 3.5 times higher than that for CF or radicals, whose radical densities were the same. The gas plasma mainly produced and CF radicals, and the CF radical density was higher in comparison to other fluorocarbon gas plasmas.

Reactive ion etching of (PZT) is demonstrated using pure gas. The variation of the etch rate with radio frequency (rf) power and process pressure has been investigated and rates up to 160 nm were obtained. The dependence of the etch rate on the plasma parameters seems to indicate an ion-induced mechanism. Analysis of photoresisterosion in the process has been performed using an atomic force microscope. It has been found that roughening of the resist surface is accelerated when high rf powers and high process pressures are used. Based on these studies a recipe for PZTetching with a photoresist mask is discussed.

The respective roles of electrons and oxygen atoms in the plasma enhanced chemical vapor deposition of -like films are investigated in a low-pressure radio-frequency helicon oxygen/tetraethoxysilane (TEOS) plasma. The plasma and film growth are monitored by optical emission spectroscopy and in situspectroscopic ellipsometry, respectively. The variations of the atomic oxygen density [O] (measured by actinometry) and the deposition rate are studied as a function of the organosilicon fraction in the plasma. First, on the basis of these measurements and the data available in the literature, it is established that electrons have the key role in TEOS fragmentation while the contribution of O is shown to be very weak. Second, it is shown that organosilicon filmsdeposited in a TEOS rich plasma are etched by O atoms when exposed to a pure oxygen plasma. The etching rate is proportional to [O] and is of the same order of magnitude than the deposition rate, which demonstrates that deposition and etching really compete in /TEOS plasma.

Continuous wave (cw) and equivalently powered, pulsed radio frequency plasmas are used to depositfilms.Films produced from and gas mixtures were analyzed with Fourier-transform infrared, x-ray photoelectron spectroscopy, scanning electron microscopy, and profilometery. Gas-phase plasma species were identified using optical emission spectroscopy. The effects of biasing (±1000 V) and grounding the substrates, pulse peak power, pulse on time and off time, and duty cycle on film composition were examined. Filmsdeposited with cw plasmas show an increase in hydrogen incorporation compared to filmsdeposited in the pulsed systems. In the pulsed plasmas,deposition rates depend on both the on time and off time of the plasma pulse cycle, while grounding the substrate causes a significant reduction in oxidation rates for filmsdeposited under all conditions.

Plasma etching of silicon is one of the important etching processes used in modern integrated circuitmanufacturing and micro-electro-mechanical systems fabrication. A good understanding of this process leads to better models which are the key to easier and less costly plasma etching process design. The main focus of this paper is on the simulation of the ion reflection from feature sidewalls and the resulting microtrenches. Pure plasma was used for experiments because of the simple chemistry. SPEEDIE (Stanford etching and deposition profile simulator) was used in this work. Langmuir adsorption model was used for etching kinetics. Self-consistent calculations were done for fluxes using surface coverage dependent sticking probabilities. For ion reflection, it was assumed that the reflected ions come off with a distribution about the specular reflection angle. This distribution is modeled as cosnθ (θ is the deviation from the specular angle) and is important in getting the correct shape for microtrenches in simulations. A three-dimensional (3D) calculation of the reflection flux was done taking into account the 3D angular distribution of the incoming ions. The ion reflection efficiency was deducted from the silicon ion enhanced etching yield versus ion angle of incidence data. The simulation results match the experimental profiles fairly well.

Selective etching of over polycrystallinesilicon has been studied using in an inductively coupled plasma reactor (ICP). Inductive powers between 200 and 1400 W, as well as pressures of 6, 10, and 20 mTorr were used in this study of the etch rate and selectivity behaviors for silicon dioxide, silicon, and passively deposited fluorocarbon films. Using in situellipsometry, the etch rates for all three of these materials were obtained for a self-bias voltage of −85 V, as well as passive deposition rates of fluorocarbon films.X-ray photoelectron spectroscopy has been used to examine the composition of steady-state fluorocarbon films present on the surfaces of polycrystallinesilicon, and silicon dioxide during etching at high and low inductive powers. The dependence of the siliconetching behavior is shown to be clearly linked to the fluorocarbon polymerization and etching behavior. Thus, the polymerization and etching behavior of the fluorocarbon is the overwhelming parameter that governs the etch selectivity process within the ICP. Selectivities of oxide to silicon are determined to increase with the inductive power, and are found to be the highest at the intermediate pressure of 10 mTorr. While the stoichiometry of the fluorocarbon films are critical factors in determining the overall etch rate behavior, the fluorocarbon film thickness on the polycrystalline and crystalline silicon is the dominant factor in determining the over siliconetch selectivity. The mechanisms involved in attaining high selectivity are dominated by a defluorination of the fluorocarbon steady-state film on polycrystallinesilicon, while maintaining a high ion current to the wafer.

Two-dimensional images of two-frequency capacitively coupled plasma in Ar and in an axisymmetric parallel plate reactor are investigated by using optical emission spectroscopy. Spatially averaged electron density is obtained by microwave interferometry. Results are presented in the form of 2D profiles of the net excitation rate of and used as a probe. Large area uniformity of plasma production driven at very high frequency (VHF) (100 MHz) and that driven at high frequency (HF) (13.56 MHz) at low pressure are compared and discussed under a low frequency (LF) (700 kHz) bias voltage on the wafer. The time modulation of the net excitation rate and the electron density indicate that the LF bias is considerably influential in the production of the plasma and in the confinement of high energy electrons at HF. Functional separation between plasma production in a gas phase and ion acceleration to the wafer is achieved in excited at VHF (100 MHz). The addition of a small amount of to the Ar plasma improves the uniformity of the radial profile of the excitation at HF (13.56 MHz).

The density of F in plasma could be reduced by 34% when the Si top plate was bombarded by energetic ions in a parallel-plate-type 500 MHz electron-cyclotron-resonance plasma reactor, but that in plasma was not reduced. We measured the densities of Si, and F in both plasmas as a function of ion-bombardment energy and found that F was generated from in plasma but not in plasma, and that the density decreased to a similar extent with increasing ion-bombardment energy in both plasmas. We conclude that the reduction of the F density in plasma was caused by the decrease in density and not by a direct reaction of F with Si when the Si plate was irradiated by energetic ions.

The formation and properties of diamond-like carbon (DLC) films prepared on silicon substrates at room temperature, using plasma immersion ion processing, are investigated with respect to film deposition parameters. Decreases in the reactive gas-flow ratios of to or the gas pressure were found to decrease the hydrogen content, increase the density and hardness, and improve the surface finish of the DLC films, all of which led to enhanced tribological properties. Decreasing the friction coefficient requires increasing the hardness of the film and smoothing its surface, whereas increasing the wear resistance correlates with reducing both the hydrogen content and residual stress in DLC films. High hardness and optimum tribological properties were reached as the growth of DLC films was subjected to low-energy ion impingement, which was induced by a −150 V pulsed bias from the plasma produced at low reactive gas pressures with low ratios.

Different dry etching methods were used to structuresingle crystal (100). Utilization of reactive ion beametching with caused enhancement of the etch rate, the selectivity and the step angles compared to conventionally applied Ar ion milling. The influence of the etch parameters on the surface damage was investigated by Rutherford backscattering spectroscopy/channeling studies and x-ray spectroscopy. The chemically assisted ion beametching with chlorine gas examined causes the lowest degree of surface damage but also the lowest etch rate.

Research has been conducted to investigate ways to make thinner, yet more cohesive TiN films.Plasma vapor deposition techniques were used in conjunction with electron cyclotron resonance to deposit TiN films on substrates of Inconel 718 (nickel-based superalloy). Previous parts of this investigation have focused on the relationship between process (i.e., film deposition) parameters, film microstructure, and film mechanical properties. The final part of this study extends the research focus to discuss what effect a change in the power setting of the microwaveplasma has on the resulting Meyer hardness of the TiN-coated sample. The crystal orientation and texture of these films are also discussed. Optimum hardness of greater than 46 GPa was found at low microwave power of 200 W and a substrate bias of −100 V. Lowering microwave power to 200 W more than doubled the number of (111)-oriented grains. Substrate bias of −100 V or greater resulted in a greater than twofold decrease in (200)-oriented grains.

We have developed a novel technique to deposit poly-Si films on insulating substrates in an electron cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition(PECVD) and investigated the effect of reactive species on polycrystallinesilicon (poly-Si) film formation at low substrate temperatures. The charged species incident on the substrate were successfully shut out by using permanent magnets set above the substrate in an ECR plasma. As a result, the films formed without charged species were found to have better crystallinity than those formed with charged species at a low substrate temperature of From results of the atomic force microscope, it was found that the surfaces of films formed without charged species were smoother than those of films formed with charged species at a substrate temperature of Therefore, it was clarified that the charged species deteriorated the crystallinity and the surface roughness while the neutral reactive species played an important role for improving them in the poly-Si film formation at low temperatures using the ECR PECVD method.

Magnetic neutral loop discharge (NLD) plasma is a new type for dry etching process characterized by effective coupling of the input electric field electron electron motion near the magnetic neutral loop (NL) region. Therefore, dense plasma can be produced and controlled spatially by changing the position of the NL. Uniformity was controlled by changing the radius of NL temporally during the etching using a repetition frequency of 0.1 Hz, so that the deviation of the etch rate was within 2% (3σ) on 200-mm-diam wafer. In nanoscale patternetching processes, we found that ions played an important role in very high aspect ratio profile etching. In ion-rich plasma, ZEP photoresistpatterned 20 nm space was successfully etched 800 nm in depth at the pressure of about 0.3 Pa, using and